The present invention concerns a machine for processing sheets for the production of packagings in materials such as cardboard or plastic, comprising driving means capable of driving sheets in a drive direction at a substantially constant drive speed through a processing zone situated between the entrance and the exit of the machine and processing means comprising a tooling and a counter-tooling respectively borne by a first and by a second rotary support shaft, which shafts extend transversely to the drive direction, being disposed opposite each other on either side of the path of the sheets, said processing means being designed to produce in these sheets cutouts and/or folds disposed transversely to the drive direction.
A machine of this type for processing sheets is known through patent application PCT WO 02/02305, filed by the applicant company. This previous patent application concerns the operation of the rotation of the support shaft of the tooling, which is performed so that, at the moment when the processing means cooperate with a sheet in order to make in it cutouts or folds transverse to the drive direction, the tangential speed of the tooling is equal to the drive speed of the sheet in the machine.
These measures allow the machine to be operated continuously, whereas it was previously necessary, in order to make cutouts or folds transverse to the drive direction of a sheet, to stop the latter momentarily and to actuate a cutting or creasing tool borne by a beam which can be moved perpendicularly to the drive direction of the sheets.
Although the machine described in document WO 02/02305 is satisfactory, it turns out that, in certain usage conditions, the cutting or the creasing made by the tooling borne by the first support shaft leaves traces of folds on the sheets processed in the machine. This is particularly the case where these sheets are made of corrugated board, the flutes of which are oriented transversely to the forward moving direction of the sheets, that is to say the cutting or the creasing are performed parallel to these flutes.
A corrugated board has at least two layers of paper or board, between which there is disposed at least one corrugated board, the corrugations of which form the aforesaid flutes. For example, these sheets can comprise a top or cover layer of paper, a first corrugated board, an intermediate layer of paper, a second corrugated board, and a top or inner layer of paper. In this case, if the cutting or the creasing is realized by first engaging the tooling with the top layer of paper, the folds can be formed on the bottom layer of paper.